Shield assembly for vacuum tubes



March 7, 1950 E. F. STAVER 2,499,612

SHIELD ASSEMBLY FOR VACUUM TUBES Filed Feb. 26, 1948 2 Sheets-Sheet 1 INVENTOR. [aw/sea E fTAl/EQ March 7, 1950 E. F. STAVER 2,499,612

SHIELD ASSEMBLY FOR VACUUM TUBES Filed Feb. 26, 1948 2 Sheets-Sheet 2 INVENTOR. t'ow/neo EjrAI/ z Patented 7, 1950 UNITED STATES PATENT OFFICE 7 Claims.

This invention relates to vacuum tube mount- Y ings, especially shields, and more particularly to a. shield and base clip assembly for the same.

The primary object of the present invention is to generally improve shields for vacuum tubes or electron emission tubes. A more particular object is to provide a shield and base clip assembly which will provide a good ground connection for the shield; which will anchor the shield in position on the tube; and which will lock the tube against escape from the tube socket. In

after appear in the following detailed specification. The specification is accompanied by a drawing in which:

modern radio receivers, the tubes are .often used' in horizontal and even inverted position, and there is a tendency for the tube to loosen from its socket, particularly when subjected to vibration, as in an automobile radio receiver or in a portable radio receiver. The problem has been aggravated with the adoption of miniature vacuum tubes, which have relatively thin lead-in wires projecting through the glass to act as prongs. The grip of the socket on such prongs is not comparable to that formerly provided with large diameter tubular prongs. It is, accordingly, a further object of the present invention to provide a shield assembly especially adapted for use with miniature tubes.

The tubes come in several sizes, but in each size there is a manufacturing tolerance such that the diameter of the glass envelope may vary somewhat, and the length of the glass envelope may vary somewhat. Moreover, the effective length of the tube may, for the present purpose, vary somewhat because of a difference in the reception of the tube by the socket.

One object of the present invention is to provide a shield assembly which will fit snugly around a miniature tube, and which will hold it securely in its socket despite variations in diameter and in effective length of the tube.

Other objects of the present invention are to eliminate vibration or rattling of the shield relative to the tube; to so design the shield assembly as to occupy a minimum space, so that the design of the chassis may be as compact as though the shields were not employed; to so relate the shield to the tube as to allow air circulation with consequent cool operation of the tube; to provide a shield assembly which is strong and sturdy yet light in weight; to provide a shield assembly which will require a minimum of material and relatively simple. manufacturing operations, and which is therefore low in cost; and to so design the shield assembly that it may be secured to the chassis or/and the vacuum tube socket without necessitating the use of extra eyelets or like fastening means.

To accomplish the foregoing general objects, and other more specific objects which will hereinafter appear, my invention resides in the shield and base clip elements and their relation one to another and to the vacuum tube, as will herein- Fig. 1 is a side elevation of a shield and base clip assembly embodying features of my invention;

Fig. 2 is a plan view of the base clip;

Fig. 3 is a section taken on the plane of the line 3-3 of Fig. 2 with the shield included;

Fig. 4 is a side elevation of a modified assembly;

Fig. 5 is a plan view of the base clip;

Fig. 6 is a side view of the same;

Figs. 7 and 8 illustrate the accommodation of the shield to changes in tube diameter; and

Figs. 9 and 10 illustrate the accommodation of the assembly to changes in tube length.

Referring to the drawing, and more particularly to Figs. 4, 5 and 6, the electron emission tube I2 and tube socket l4 have added thereto the combination of a metallic shield l6 and a base clip l8. The shield encloses the tube and has means, in this case an inwardly turned edge 20 at the top, to hold the tube against escape from the socket M. The base clip l8 has a part 22 which is secured to the chassis 24. This is preferably done by meansof a fastener, in this case an eyelet 26, which is anyway employed to secure the socket H to the chassis 24. The base clip further comprises an upstanding finger 28, which extends along and bears resiliently against the outside of the shield 16 for electrical contact therewith. This provides a good ground connection to the chassis.

Moreover, the shield and finger preferably have mating holding means, whereby the finger restrains the shield against longitudinal movement away from the socket. In the present case, the mating means comprises a horizontal rib 30 formed on the shield l6, and a detent 32 formed on the finger 28. The finger is preferably provided with a plurality of closely spaced detents, as shown, thereby accommodating manufacturing variations in the effective socketed length of the tube. The expression socketed length is employed because the height of the top of the tube may vary due either to a change in the length of the glass envelope of the tube, or to a change in how far the tube fits downwardly against the socket, or both.

The shield itself comprises a piece of resilient sheet metal bent to generally cylindrical configuration, with an overlap of a substantial amount, say one-quarter inch, as is shown at 40 in Fig. 7. This accommodates variations in the diameter of the glass envelope of the vacuum tube. This will be evident from a comparison of Fig. 7 with Fig. 8, the shield in Fig. 7 being applied to a tube of smaller diameter, and the shield of Fig. 8 being applied to a tube of larger diameter. The manufacturing tolerance is plus or minus of an inch, making possible a variation of inch in diameter.

Instead of the single rib 30 referred to in connection with Fig. 4, the shield is preferably provided with a series of spaced annular ribs extending entirely around the shield, as is shown at 42, l4, l6 and 48. These stiffen and strengthen the shield, and at the overlap 40 (Fig. '7) the ribs register in slidable relation. The ribs, therefore, also serve to keep the shield in true cylindrical form, and to prevent any relative displacement of one overlapping edge relative to the other in the direction of the axis of the tube.

The shield is also provided with a plurality of vertical lines of inwardly pressed projections 50. These may be vertical ridges, but most simply take the form of rounded dots or dimples, as here shown. The dimples bear against the glass envelope of the tube while spacing the shield somewhat from the tube, thus facilitating admission of air to the tube envelope, with consequent cool-- ing of the tube. The dimples also make it easy to slide the shield smoothly over the tube.

The manner in which manufacturing variations in length of the tube are accommodated, will be clear from a comparison of Fig. 9 with Fig. 10. In Fig. 9 the tube 86 is short, and the shield 88 is in lowermost position, the rib 5| being engaged beneath the lowermost detent 52 of a finger '90. (This is part of a base clip like that shown in Figs. 1 and 2.) In Fig. 10, the tube 92 is somewhat longer, and the shield 88 is somewhat higher, the rib 5| being engaged by a higher detent 54 of finger 90. The manufacturing tolerance in the length of the envelope is plus or minus of an inch, so that the total variation may be a matter of of an inch. Moreover, because of variations at the base, the chassis, and the socket, the assembly is preferably designed to accommodate a variation in effective length of say inch.

Of course, the shield is made in several lengths to accommodate difierent types of miniature tubes which have a substantial difference in length, and the modification shown in Figs. 1, 2 and 3 is shown as applied to a tube 62 which is longer than the tube l2, shown in Fig. 4. The socket 64 (Fig. 1) may be the same as the socket H, but the shield 66, while similar in construction to the shield I6, is longer. For shielding alone, the longest shield may be used with shorter types of tube. However, to hold the tube in the socket, the proper length is preferable. At present theshield is made in three lengths.

The base clip 68 illustrated in Figs. 1 and 2 is very different from the base clip l8, for in the present case the base clip extends substantially around the shield, and has a plurality of fingers upstanding from the base. More specifically, there are three fingers 10, I2 and 14, said fingers being alike and having a similar grouping of detents. The base clip is secured to the chassis by means of two eyelets I6 and 18, these eyelets preferably being the same eyelets that are employed to fasten the socket 64 to the chassis 80. The base clip may be a drawn sheet metal member, or as here illustrated, may be stamped and bent out of sheet metal, without a drawing operation. In the latter case the bottom portion of the base clip may be left open at one point, said point corresponding to the arm 12 of an adjacent base clip when a series of base clips are being stamped from a piece of sheet metal, thereby lessening waste or scrap metal.

The bottom may be provided with an upwardly pressed ridge or rib, as shown at 82 (Figs. 2 and 3),

to stilfen the same. For the same purpose, the bend at the base of the fingers 10, 12 and It may be provided with an inwardly pressed vertical groove or indentation, as shown at 84 (Figs. 1 and 3).

The shield-may be made of aluminum, or of steel coated with tin plate or nickel plate. The base clip may be made of spring brass, or may be made of tempered spring steel, with a coating of tin plate or nickel plate. These are examples, and not exclusive.

It is believed that the construction and method of use, as well as the advantages of my improvedshield assembly for vacuum tubes, will be apparent from the foregoing detailed description. The shield fits snugly on the smallest tube of a particular type or size, yet expands to provide a snug fit on a larger tube of same type or size, thus automatically compensating for manufacturing tolerance in the diamter of the tube. The multiple serrations on the base clip not only lock the shield and tube against longitudinal movement, but automatically compensate for variations in tube length. The base clip is mounted on the chassis by means of the same eyelets or other fastening means as are employed to hold the socket on the chassis. The three vertical rows of dimples on the shield provide a gentle but firm snug fit against the tube, thus avoiding vibration, rattling or microphonics. At the same time, there is no danger of undue pressure or tube breakage. The assembly employes a minimum of metal, and is light in weight yet sturdy and serviceable. The space requirements have been minimized so that the chassis design may be made as compact as though the shields were not employed. This is particularly important when dealing with miniature tubes. The dimples space the shields somewhat from the tube, and afford air circulation and cool operation. While not necessary, the inner surface of the shield may, if desired, be given a blackened surface for maximum heat transfer and cooler operation.

It will be understood that closely spaced ribs may be used with one detent, instead of closely spaced detents with one rib. Also the shield may be provided with detents, instead of ribs. The base clips may be used with a drawn or seamless shield, instead of the lapped shield here shown. The base clip may be a closed drawn ring, instead of an open bent ring as here shown.

The dimples may vary in number. In the three lengths of shield which I now make, the shortest has three sections between four ribs, and dimples are provided in the first and third sections. The next length has four sections between five ribs, and dimples are provided in the first and fourth sections. The third length has six sections between seven ribs, and dimples are provided in the first, third and sixth sections from the bottom. However, it will be understood that different numbers and different location of the dimples may be provided. The sheet metal for the shield may have a thickness of, say, 0.010" if aluminum and 0.009" if tin plated steel. The single prong clips may be made of sheet metal having a thickness of 0.015" if made of nickel plated tempered spring steel. The three pronged base may be made of half-hard brass having a thickness of 0.015" with a finish of tin or nickel plate. The spacing between ribs in the examples shown is one-quarter inch. The overall length of the shields may be +5" with an inside diameter at the dimples of 0.690" for short tubes, such as SAKS. 6AL5.etc.; alength of 1.75" and an inside diameter at the dimples of 0.690" for long tubes, such as 6AQ5, 6X4, 35W4 and 50B5; the same inside diameter and a length of 1 A" for medium length tubes, such as IE5, 6AC5, 6BE6, 6C4, 6AT6; and the same inside diameter and a length of 1%" for medium tubes, such as 1R5, 6AG5, 6BE6, 604 and 6AT6; a length of 1%" and an inside diameter at the dimples of 0.80" for tubes having nine base pins, such as 12AT7.

It will be understood that the dimensions and quantitative values are given solely by way of example, and are not intended to be in limitation of the invention.

It will be apparent that while I have shown and described the invention in several preferred forms, many changes may be made in the structures shown without departing from the spirit of the invention, as sought to be defined in the following claims.

Iclaim:

1. For use with an electron emission tube and socket, the combination of a metallic shield and a base clip, said metallic shield having an inturned flange at the top for bearing directly against the top of a tube to hold the tube against escape from its socket, said base clip being made of sheet metal and having a base portion dimensioned to be secured to a chassis and an upstanding finger extending along and bearing resiliently against the outside of the shield for electrical contact therewith, said shield and finger having mating holding means whereby the finger restrains the shield against longitudinal movement away from the socket, said mating means comprising one or more horizontal ribs and a plurality of detents, said detents being relatively closely spaced in order to accommodate manufacturing variations in the effective socketed length of the tube.

2. A combination as defined in claim 1 in which the ribs are annular ribs extending entirely around the shield, and in which the closely spaced dleltents are provided on the finger of the base 0 D.

3. A vacuum tube shield for use with electron emission tubes, said shield comprising a single piece of sheet metal bent to generally cylindrical configuration with overlapping edges having an overlap of a substantial amount to accommodate tolerance variations in diameter of the glass envelope of the vacuum tube, said shield being provided with a plurality of vertical lines of inwardly pressed smooth projections or dimples to bear against the glass envelope of the tube while .spaclng the shield somewhat from the tube.

4. A vacuum tube shield for use with electron emission tubes, said shield comprising a single piece of sheet metal bent to generally cylindrical configuration with overlapping edges having an overlap of a substantial amount, say one-quarter inch, to accommodate variations in diameter of the glass envelope of the vacuum tube, the top edge of said shield being turned inwardly over the cylindrical configuration with overlapping edges having an overlap of a. substantial amount to accommodate tolerance variations in diameter of the tube, the top edge of said shield being turned inwardl over the top of the tube, said shield having a plurality of outwardly pressed annular ribs which stiffen and strengthen the shield, said ribs registering slidably at the overlap, said base clip being made of sheet metal and having a base portion adapted to be secured to a chassis and an upstanding finger extending along and bearing resiliently against the outside of the shield for electrical contact therewith, said shield and finger having mating means whereby the finger restrains the shield against longitudinal movement away from the socket, said mating means comprising one of the aforesaid stiffening and registering ribs on said shield and a detent on said finger.

6. For use with an electron emission tube and socket, the combination of a metallic shield and a base clip, said metallic shield comprising a piece of sheet metal bent to generally cylindrical configuration with an overlap of a substantial amount to accommodate manufacturing variations in diameter of the tube, the top edge of said shield being turned inwardly over the top of the tube, said shield having a plurality of outwardly pressed annular ribs which stiffen and strengthen the shield, said base clip being made of sheet metal and having a base portion dimensioned to be eyeletted to a chassis and an upstanding finger extending along and bearing resiliently against the outside of the shield for electrical contact therewith, said shield and finger having mating means whereby the finger restrains the shield against longitudinal movement away from the socket, said mating means comprising one of the aforesaid ribs on said shield and one or more detents on said finger, said detents being relatively closely spaced in order to accommodate manufacturing variations in the socketed length of the tube, whereby the top of the shield may cooperate with the top of the tube without necessitating the use of resilient means therebetween.

7. A vacuum tube shield for use with electron emission tubes, said shield comprising a single substantially rectangular piece of resilient sheet metal bent to form a cylinder of substantially uniform diameter with only two overlapping edges having an overlap of a substantial amount to accommodate tolerance variations in diameter of the glass envelope of the vacuum tube, said shield having a plurality of continuous annular ribs which stiffen and strengthen the shield, said ribs being channeled in the sheet metal and extending all the way from edge to edge, and said ribs registering slidably at the overlapped edges of the shield.

EDWARD F. BTAVER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,036,709 MacLaren Apr. 7, 1936 2,050,885 Hafecost et al Aug. 11, 1938 0.913 Hafecost et al May 18, 1937 2,358,491 Del Camp Sept. 19. 1944 FOREIGN PATENTS Number Country Data 515.55]. Great Britain Dec. 7, 1988 

